I am administrating a small server for LAN, providing basic services such as web-proxy, ldap, kerberos, afs, etc. Yesterday there was a power cut so server halted. When I restarted it no network interfaces were available and configured. I tried restarting networking daemon but it just exited with 0 status. So I tried to run one of the interfaces manually, but ifup and ifdown commands simply are not there. No only in PATH, but they disappeared from /sbin.

1 Answer
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Are there any messages in /var/log/messages, /var/log/syslog, /var/log/boot.log, etc. indicating an I/O error or an error mounting a partition or an error activating LVM or MD or RAID?

Was there a "Filesystem unclean" or "fsck" message when the server powered up?

Are all partitions currently mounted? Are there any files in /sbin?

To fix the exact problem you mention, assuming all partitions were correctly mounted, I would boot from a Debian boot CD in recovery/rescue mode, start a shell, find where your /sbin (or probably the / (root)) partition is mounted, then run chroot <that path> /bin/bash, then you can run sudo apt-get install ifupdown to re-install /sbin/ifup, then reboot.

But you should try to find out if anything else is broken. Try installing debsums, i.e. sudo apt-get install debsums.

Great answer! I fixed the problem by simply reinstalling the ifupdown packages, but still don't know what exactly happened to it. No logs indicate any possible causes and another applications seem work finely...
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RizoJan 12 '11 at 22:45